1. Field of the Invention
This invention relates to a novel polymeric composition. More particularly, this invention relates to curable compositions comprising blends of one or more phenolic resins, one or more thermoplastic polymers having active hydrogens, and one or more curing agents which are capable of curing the phenolic resins and capable of reacting with the reactive hydrogens of said polymer forming an interpenetrating network in which the polymers are linked to the cured resins by way of the residues of the curing agents.
2. Prior Art
Phenolic resins are a class of synthetic materials that are produced by the reaction of phenols with aldehydes. The starting materials for use in the manufacture of phenolic resin which are used in greatest volume are phenol and formaldehyde. Other important phenolic starting materials include alkyl-substituted phenols such as cresols, xylenols, p-tert-butyl-phenol, p-phenylphenol, nonylphenol, and the like. Also diphenols, e.g., resorcinol (1,3-benzenediol) and bisphenol-A [bis-A or 2,2-bis(4-hydroxylphenyl)propane], are used in smaller quantities for applications requiring special properties. In addition to formaldehyde, acetaldehyde or furfuraldehyde are also employed as aldehyde starting materials, but in much smaller quantities. The greater latitude in molecular structure for phenolic resins, has resulted in an array of physical properties for these resins allowing use in a larger number of applications.
Key innovations in early phenolic resin manufacture included control of the molecular structure and the use of heat and pressure to achieve desirable properties. Studies in the use of acidic or basic catalysts and of changes in the molar ratio of formaldehyde to phenol resulted in the definition of two classes of phenolic resins, namely novolac or novolak resins and resol resins. Resol resins are made with a molar excess of formaldehyde under alkaline conditions. Novolac resins are normally prepared with a molar excess of phenol under acidic conditions. Thus novolacs are thermoplastic and require an additional curing agent, the most common being hexamethylene-tetraamine. Other least common curing agents are materials such as epoxy, isocyanate and, carboxylic acid containing compounds which can react the active hydrogen atom in the hydroxyl group present in phenolic resins.
Phenolic resins have many uses because of their excellent properties such as electrical properties, high thermal stability and low flammability. However, phenolics suffer from several drawbacks which restrict their utility. Phenolics are generally highly brittle, hence have low impact strength. In the prior art, attempts have been made to remedy or improve some of the drawbacks by utilizing various modifiers such as additives, plasticizers and fillers or by modifying the chemical structure of phenolics. The modifiers proposed in the art include a variety of classes of materials ranging from natural oils to thermoplastics, and vary depending on the properties to be improved. In many cases success has been spotty, and some properties are improved, while other properties have deteriorated. The use of plasticizers, thermoplastics or elastomers in phenolic resins has been successful to some degree in improving the flexibility of phenolic resins. However, those materials are required in large amounts, often exceeding the amount of phenolic resin. Addition of these large amounts of additives results in a deterioration in properties, such as a deterioration in material (mechanical) strength, heat and chemical resistance mainly because of phase separation due to poor compatibility between the additives and the phenolic resin. Use of compatable modifiers have lessened the adverse impact, however, problems still remain.
As means of improving phenolic resin properties, there have been proposed numer of setting type compositions formed by incorporating various reinforcing materials including various types of polyamide resins. For example, U.S. Pat. Nos. 4,173,290 and 3,496,248; Japanese Patent Publication Nos. 59/159,872; 59/133,045; and 55/108,482; and USSR. Patent Publication Nos. 730,750 describe various adhesive compositions in which a phenolic resin and a polyamide resin are used. Japanese Patent Publication No. 49,001,814 describes methods of preparing phenolic fibers containing a polyamide for improved spinnability and tenacity. Also, Japanese Patent Publication No. 58/176,236 describes phenolic compositions containing a polyamide resin for improved moldability and improved properties.
Polyamides are well known and defined as polymers which contain recurring amide groups (--CO--NH--) in the main polymeric backbone. There are two types of synthetic polyamides, i.e., those prepared from a diamine and a diacid; and those prepared from an amino acid or amino acid derivatives. Nylon 66 is an example of the first type, and nylon 6 is an example of the second type. Depending on the starting materials, various polyamide structures are possible. The properties of polyamides vary depending on the structure. The linear aliphatic polyamides are capable of fiber formation and are thus widely used for fiber production. Such linear aliphatic polyamides are also used as engineering plastics. Various aromatic polyamides have been used in high temperature applications because of superior thermal stability as compared to the linear aliphatic polyamides.
Various references disclose mixtures containing phenol formaldehyde and polyamide resins. For example, USSR Pat. No. 639,831 describes a concrete mixture containing phenol formaldehyde and polyamide resins and furfuryl alcohol. U.S. Pat. No. 4,244,858 describes auto extinguishing thermoplastic polyamide compositions containing a polyamide, an alkali and/or ammonium polyphosphate, mineral reinforcing agents and/or fillers and phenol-aldehyde resin. USSR Pat. No. 634,968 describes a material containing phenolshalin-phenolformaldehyde resin, silvery graphite, polyamide resin and sawdust which is useful as an antifriction self-lubricating molding material. U.S. Pat. No. 4,110,277 describes the production of an infusible phenolic fiber by melt-spinning a fusible uncured phenol-(pain) formaldehyde resin followed by curing the product at least to the point of infusibility, the improvement comprises incorporating into the resin prior to the spinning 5-30% of an aliphatic nylon. Germany No. 2800467 describes a self-extinguishing thermoplastic polyamide composition containing 40-95 wt% polyamide, 0-50% reinforcing agent and/or filler, 0.5 to 20 wt% phenol aldehyde condensation resin, 0.2-12 wt% phosphoryl nitride oxide and/or precursors of phosphoryl nitride containing 20-50% phosphorus, 15-23% Nitrogen, 45-26.2% oxygen, 12-0% carbon and 8-0% hydrogen. Japan Pat. No. 50/142,816 describes blends of 50-99 wt% thermoplastic phenolic resins, and 1 to 50 wt% polyamide which are melt spun and crosslinked to give fire-resistant infusible fibers, and Japan Pat. No. 51/109057 describes molding compositions of improved nonflammability manufactured from aromatic polyamides, phosphorus containing phenol resins and at least one amide solvent. Japan No. 51/073559 describes polyamide compositions containing 1-90 parts by weight of a phenol-formation low-condensate and 100 parts by weight of a polyamide resin, and Japan No. 55/147556 describes a thermosetting resin molding material containing a thermoset resin such as a phenol resin, melamine resin, and urea resin, and a nylon type plasticizer. Japan No. 57/003877 describes a thermoset adhesive comprising an alcohol soluble polyamide resin, alcohol soluble phenol resin, water soluble epoxy resin and a curing agent for water-soluble epoxy resin and Germany No. 2700092 describes phenol-formaldehyde resin and polyamide terpolymer impregnated prepegs with reduced flame spread, smoke formation and toxic gases on burning. Japan No. 48/072413 describes fibers of phenolic resin blends comprising novolak resins and 3 to 30% of a polyamide, polyurethane or cellulose derivative. Mixtures or adducts containing polyamide or polyepoxide resins are known. For example, U.S. Pat. No. 3,462,337 describes adhesive compositions which comprise a synthetic linear polyamide and polyepoxide for use as side seam adhesive for metal cans.